Heat exchanger and heating apparatus provided therewith

ABSTRACT

A heat exchanger, provided with a body with at least one flue gas channel and at least one water carrying channel, at least one burner space and at least one flue gas discharge, wherein the at least one flue gas channel extends at least partly between at least a burner space and at least one flue gas discharge and at least a portion of the at least one flue gas channel comprises at least one porous or gas-transmissive heat exchange element.

The invention relates to a heat exchanger.

It is known from practice to manufacture heat exchangers for, forinstance, heating apparatus, hot water supplies and the like from, forinstance, steel or iron or light metal such as aluminum. As a rule, acasting method is applied here. Casting techniques offer a relativelylarge design choice but complex casting moulds. As a rule, in existingheat exchangers, heat transfer increasing elements are provided in aflue gas channel, which elements are cast integrally in the castingmoulds, at least when casting techniques are used. The heat transfer isthen not always optimal.

The object of the invention is to provide a heat exchanger.

In a first aspect, a heat exchanger according to the invention ischaracterized in that a body is provided with at least one flue gaschannel and at least one water carrying channel, at least one burnerchamber and at least one flue gas discharge, wherein the at least oneflue gas channel extends at least partly between the at least one burnerspace and at least one flue gas discharge, and at least one portion ofthe at least one flue gas channel comprises at least one porous or gastransmissive heat exchange element.

Herein, a porous or gas transmissive heat exchange element is understoodto mean an element with a structure and/or manufactured from a materialwith continuous openings, such that gas can flow through the heatexchange element(s), from, in flow direction, a side proximal to theburner space to a side proximal to the flue gas discharge. The openingscan comprise, for instance, pores and/or channels.

Preferably, in the flow direction of the flue gases, the porosityincreases and/or the density decreases of the heat exchange element or,if several heat exchange elements or parts thereof are providedsuccessively in the flow direction, of the successive heat exchangeelements, or parts thereof, so that the flow resistance decreases andthe heat transfer can be further optimized. For instance, a first partof the heat exchange element, or with several successive elements, afirst heat exchange element, adjacent the burner space, can have arelatively low porosity and high density, for instance a density of morethan 70%, while a second part of the heat exchange element or, in flowdirection, a trailing second heat exchange element, can have arelatively low density and high porosity, for instance a porosity ofmore than 70%. Preferably, especially in this manner, at least twosuccessive zones are formed in the flue gas channel, with differentaverage porosity and/or density. These values mentioned should not betaken as being limitative in any manner and serve merely as an example.On the basis of the further design of a heat exchanger, a skilled personcan chose and calculate suitable values.

Independently of the first aspect of the invention, and according to asecond aspect, the invention provides a first part of a heat exchangeelement wherein the minimal thicknesses and/or cross-sections of the atleast one heat exchange element of the first part are, in fact, greaterthan those of the at least one heat exchange element of the second part.This serves the purpose of providing a more massive first heat exchangeelement, which can resist the high temperatures of the combustion gases.

In a third aspect, a heat exchanger according to the invention ischaracterized in that the or at least one heat exchange element ismanufactured at least partly utilizing metal foaming. Preferably, theentire, or all heat exchange elements that are placed in a flue gaschannel are manufactured utilizing metal foaming.

Alternatively or additionally, the at least one heat exchange elementcan comprise fibers, in particular metal fibers.

Such fibers can be from, for instance, metal or ceramics and beprocessed into a porous mass, for instance a woven or non-woven element.The fibers ensure a relatively large contact surface in relation to thevolume, in particular if the fibers are relatively thin, for instance anaverage thickness of less than 1 micrometer to a few tens or hundreds ormicrometers. Preferably, the fibers have an average thickness of between0.5 and 200 micrometer, more particularly between 0.5 and 50 micrometer.

In an advantageous manner, a heat exchange element can be utilized thatis at least partly wintered.

In a fourth aspect, a heat exchanger according to the invention ischaracterized in that body parts are provided which are manufactured atleast partly through extrusion or through casting techniques. Lightmetal, such as aluminum or an alloy thereof, can then be utilized.

In a fifth aspect, the invention is characterized in that at least one,and preferably each body part is provided with recesses, in particularon a side remote from the flue gas channel, in which parts of a secondwater carrying channel part are formed or included.

The aspects mentioned and other aspects of the invention can be utilizedseparately as well as in combination.

The invention further contemplates providing a body part for such a heatexchanger, and a heat exchange element therefore.

The invention furthermore contemplates providing a method for themanufacture of a heat exchanger.

In a first aspect, a method is characterized in that at least two bodyparts are formed, in particular through extrusion or casting techniques,which body parts each comprise at least a portion of a water carryingchannel part, which body parts are mutually connected by end partsand/or at least one heat exchange element, such that the body parts arethus held at a mutual distance from each other while forming a flue gaschannel in which said at least one heat exchange element extends, andpreferably the water carrying channel parts in the two body parts aremutually connected.

Alternatively, one body part can be utilized in which the entire fluegas channel is formed, which is at least partly filled with at least oneat least partly porous or otherwise gas transmissive heat exchangeelement.

The invention will be further elucidated on the basis of exemplaryembodiments, with reference to the drawing. In the drawing:

FIGS. 1A and B show, in front and side view, a heat exchanger withoutside parts;

FIG. 2 shows, in perspective view, a heat exchanger according to FIG. 1;

FIG. 2A shows, in slight enlargement, a part of a heat exchangeraccording to FIG. 2;

FIG. 3 shows, in front view, a heat exchanger, in a second embodiment,without side parts;

FIG. 4 shows, in perspective side view, a heat exchanger according toFIG. 3;

FIG. 4A shows, in slight enlargement, a portion of a heat exchangeraccording to FIG. 4;

FIG. 5 shows, in perspective view, a body part for a heat exchangeraccording to FIGS. 1-2;

FIGS. 5A and 5B show embodiments of a heat transferring elementaccording to the invention;

FIGS. 5C and 5D schematically show, in side view and front view, analternative embodiment of a heat transferring surface increasingelement;

FIG. 6 shows, in perspective view, a body part for a heat exchangeraccording to FIGS. 3-4;

FIG. 7 shows, in side view, an alternative embodiment of a heatexchanger according to FIG. 1; and

FIG. 8 schematically shows a heating apparatus with a heat exchanger, inparticular according to FIG. 7.

The invention is described on the basis of a number of embodimentsthereof. These are not to be construed to be limitative in any manner.In particular, also, combinations or parts of the embodiments shown andloose parts thereof are understood to fall within the invention.Furthermore, variations thereon are understood to be also representedherein.

In FIG. 1A, in front view, and in FIG. 1B in side view, as well as inFIG. 2, a body 1 of a heat exchanger 1 is shown, assembled from two bodyparts 3, 4 and a burner hood 5 with burner deck 6. The body parts 3, 4and preferably also the burner hood 5 are preferably manufactured fromaluminum or an alloy thereof, although they can also be manufacturedfrom other material, such as iron or steel. In an advantageousembodiment, the body parts 3, 4 are manufactured substantially throughextrusion. This is a simple and relatively inexpensive manufacturingmethod. However, casting is an option too. Especially in the extrudedembodiment, the body parts 3, 4 have a substantially constantcross-section in one direction, in FIGS. 1A and 3 at right angles to theplane of the drawing.

In FIG. 1, adjacent a first end 7 of the body 2, the burner hood 5 issecured, for instance by screws 8, while the burner deck 6 is confinedbetween the burner hood 5 and two flanges 9 extending in two directionsat the end 7. Optionally, a suitable gasket (not shown) may have beeninserted for a flue gas-tight sealing. In the burner hood 5, a centralopening 10 is provided, through which, during use, gas or a gas/airmixture can be introduced to be burned, so that heated flue gases areobtained, formed in a flue gas channel 11 between the two body parts 3,4 as will be described hereinafter.

In this embodiment, the body 2, in particular the body parts 3, 4 eachcomprise a first part 12 and a second part 13, which here, link up witheach other. The first part 12, viewed in front view as in FIG. 1A, has ameandering configuration. To that end, each of the body parts 3, 4comprises a series of bends 14, in the embodiment shown four bends14A-D, 15 A-D, respectively. In this embodiment, the meanderingconfiguration is designed so as to be somewhat sinusoidal. Each bodypart has an outside 16 and an opposite side 17 proximal to the flue gaschannel 11. The meandering first part can therefore have elevations 18and lows 19. Here, as elevations 18 are seen the parts located furthestfrom a central plane V, and, as lows, the parts located therebetween. Ascentral plane V, a plane V can be seen, extending approximately midwaybetween two imaginary planes V1 and V2, with the planes V1 and V2extending parallel to each other over the elevations 18 located furthestfrom the plane V of the respective body parts 3, 4. In this first part,the configuration of the body parts 3, 4 and the channels 11 is, infact, a zigzag configuration so that a large heat transferring surfacecan be obtained in a compact space. It is noted that the first part 12can also have a different, for instance straight configuration, in thesense that no bends or meanderings are included, while the first part 12and the second part 13 have a parallel flow direction, or can mutuallyinclude an angle. Then, with the construction height remaining the same,in principle, the length of the flue gas channel 11 in the flowdirection from the burner space B to the flue gas discharge R will besmaller than in an embodiment where indeed a meandering part 12 isincluded, but a reduced flow resistance can be formed.

In this embodiment, the second part 13 of the each body part 3, 4 has asubstantially straight form, with an outside 16 and an opposite side 17proximal to the flue gas channel 11. In this embodiment, the plane Vextends midway between these two body parts 3, 4. However, this may alsobe offset over a distance relative therefrom, to the left or the right,in side view. On the side 17 proximal to the flue gas channel part 11,in the second part 13, on each body part 3, 4, one or a plurality ofheat transferring surface increasing element(s) 20 is/are present orprovided thereon, fastened thereon by, for instance, gluing, welding,forcing, clamping, sintering, soldering or fastened in a differentmanner, which element(s) form heat exchange elements. Also the or eachheat exchange element can be clamped between the two parts 3, 4. Theheat exchange element(s) extend(s) in the flue gas channel 11 and/orpartly define this, and are porous or gas transmissive such that, duringuse, flue gases can flow through the or each heat exchange element whileexchanging heat. As a result of the porosity or the gas transmissivityof the elements 20, a greater contact surface is obtained between heatedflue gases in the flue gas channel 11 and the surface 17 and/or heattransfer increasing elements provided thereon. If several heat exchangeelements are utilized, they can be placed both one behind the other andside by side in flow direction.

In the first part 12 of the flue gas channel 11 too, one or more heatexchange elements 20 can be provided, preferably with a porosity that ishigher than that of the or a heat exchange element 20 in the second part13.

Herein, porous is at least understood to include manufactured from amaterial and/or with a method such that open pores are provided that arein communication with each other and are, for instance, continuous.Herein, gas transmissive is at least understood to include an elementprovided with channels or such continuous openings through which fluegases can flow, while exchanging heat to the environment, in particularto the respective element, such as for instance foams, fins, fiber mat.The porosity and density can be expressed in a percentage, while withporosity, the percentage represents the part of the volume not filled bythe solid material such as metal and, hence, suitable for through-flowby flue gases. For the density, the percentage signifies the part formedby the solid material.

In an advantageous embodiment, the or each heat exchange element 20 isat least partly formed through metal foaming, as schematically shown inFIG. 5B, so that a porous mass is obtained that can be manufactured orbrought into a desired form, for instance by mechanical and/or removingoperations. With it, an optimal shape for the heat exchange elements canbe obtained, with optimal abutment against the inside 17 of the secondpart 13. Metal foam can offer a relatively robust element that may beconstructively advantageous and can ensure a good heat exchange betweenthe flue gases and the metal, and a good transfer to the elements 3, 4.As a technique, metal foaming is sufficiently known from practice, asare the means to then create and influence, for instance, porosity, sothat in each part of an element obtained through metal foaming, adesired predetermined porosity can be achieved, in any case on average.

In an alternative embodiment, fibers are used for the heat exchangeelement, as schematically shown in FIG. 5A, for instance metal fibers orceramic fibers. A woven or non-woven element can, for instance, beformed therefrom. In an alternative embodiment, the elements 20 can beat least partly formed by removing or non-removing operations of thebody parts or, when for instance a casting process is utilized forforming the body parts, through integral forming, in particular casting,during manufacture, while for forming the elements, gas can for instancebe blown through the liquid material. Also, ribs can be extruded.Alternatively or additionally, porous and/or gas transmissive materialscan be used, such as metals or ceramic filling materials. In thedrawing, the heat transferring surface increasing elements arerepresented in a simplified manner as rectangles. The design of suchelements can simply be selected by skilled person.

Fibers for an element 20 according to the invention can be at leastpartly manufactured through drawing or extrusion, in particular throughbundle drawing or multi fiber extrusion, through hot drawing from a weldpool, through cold or through hot rolling, a removing and/or pressingtechniques and/or through foaming or blowing. The or a heat exchangeelement can at least partly be manufactured from a woven or a non-wovenmaterial, for instance from fibers, in particular metals and/or ceramicfibers. It is preferred that a heat exchange element 20 according to theinvention is at least partly sintered, so that an element is obtainedwhich is heat and moisture resistant and can be placed as a unit.

In a heat exchanger according to the invention, use is preferably madeof zones that succeed each other in flow direction s, in which zones theheat exchange can be different. To that end, the porosity or density ofthe respective heat exchange element 20 or part thereof extending in arespective zone I, II, can deviate from that in a different zone. InFIG. 1, two zones I, II are shown. However, several zones can beprovided too and the first zone can for instance extend in the firstpart 12 and the second zone in the second part 13, as shown in FIG. 1,or both zones I, II can extend in the second zone 13 as shown in FIG. 3,with the first part 12 not comprising a porous heat exchange element. Byway of illustration, the first zone I can for instance have a porosityof less than 70%, and a relatively high density of, for instance, morethan 70%, for instance 95%, while then, the second zone II has, forinstance, a relatively low density, for instance less than 70%, and arelative high porosity, such as over 70%, more particularly for instance95%. As a result, the flow resistance will decrease in flow direction.In the first zone, during use, heated flue cases will give off thegreatest part of the heat, be cooled from, for instance, well over above1000° C., for instance approximately 1600° C., to well over 1000° C.,for instance to approximately 450° C. In the second zone, the heatexchange will be continued so that the flue gases can be cooled downfurther, for instance to a condensing temperature.

The use of metal foaming offers the advantage that a heat exchangeelement clamped only against the parts 3, 4 ensures a particularly goodheat transfer when compared to, for instance, fins or plate parts. Forobtaining a changing porosity and/or density, different heat exchangeelements with different porosities and/or densities can be placed sideby side and/or one behind the other, or the porosity and/or density in aheat exchange element can be varied.

In the first part 12 and the second part 13, parts 21 of a watercarrying channel 22 are provided. In the exemplary embodiment shown,these parts 21 are all tubular with a constant cross-section, which havea longitudinal direction L, approximately at right angles to the planeof the drawing in FIGS. 1A and 3, which longitudinal direction L isparallel to an extrusion direction for the body parts, if these areextruded. Adjacent the first end 7, in each body part 3, 4, a first part21A is provided as the beginning of the meandering first part 12,directly below the burner deck 6. Then, two parts 21B are provided inthe second part 13. Preferably, the channel parts 21 on both sides ofthe flue gas carrying channel 11 are mutually connected for forming achannel 22 circumventing the heat exchanger, but, optionally, thechannel parts on both sides of the flue gas carrying channel 11 canalso, each, form a channel part 22 that can be used for, for instance,different heat exchange circuits, or be mutually connected outside theheat exchanger 1.

In the channel parts 22, also, heat transferring surface increasingelements can be utilized which can be integrally formed especiallythrough extrusion, while the channel parts themselves need not bedivisible, while to that end, also, porous materials and/or elements canbe used as described hereinabove.

It is preferred that the channel parts 21 are mutually connected throughend hoods 24 and connecting channel parts extending therein (FIG. 8).These end hoods 24 may further comprise the connections for the heatingcircuits, gas and air supply pipes and the like. The end hoods cansimply be fastened, with interposition of suitable gaskets, against thesides of the parts 3, 4 arranged side by side, so that a flue gaschannel 11 closed towards the sides and a continuous water channel 22 orwater channels 22 are obtained, while furthermore, the parts 3, 4 areheld in a suitable position and at a suitable distance.

With the embodiment shown, the channel parts 21 are provided on theoutside of the parts 3, 4, so that the sides thereof facing inwards,i.e. towards the flue gas channel 11, can be designed to be relativelyflat, at least without protrusions formed by the channel parts. Theycan, however, also be positioned differently, for instance partlyoutside and partly inside the flue gas channel 11 or entirely inside theflue gas channel 11. This holds both for the individual channel partsand for the assembly thereof. Preferably, the or each channel 22 is laidout such that it can function in counterflow to the flow direction ofthe flue gases through the flue gas channel 11, so that an improvedefficiency can be obtained. To that end, for instance, the through-flowopening in the different channel parts can be adjusted in order togenerate a flow speed change in the channel, for a further optimisationof the heat exchange.

At the underside of the heat exchanger 1, a foot 23 is provided on whichthe heat exchanger can be mounted.

In FIGS. 3 and 4, an alternative embodiment is given of a heat exchangeraccording to the invention, wherein, substantially, only those parts aredescribed that deviate from the other embodiments. Further, reference ismade to the further description, in particular of FIGS. 1, 2 and 8. Inthis embodiment, each of the parts 3, 4 in the first part 12 has ameandering flow gas channel part 11A formed between bends 14A-D, 15A-Drespectively, formed such that five flue gas sub channel parts 11A¹-11A⁵are obtained, which are mutually connected by bend parts 11B and extendapproximately parallel to each other. In the first part 3, in the firstbend 14A, two water channel parts 21 are included, parallel to eachother, located at a distance D from each other, between a relativelywide first flue gas sub channel part 11A¹ linking up with the burnerdeck 6 of the burner 5 and a second flue gas sub channel part 11A²located therebeneath, respectively, and between a third flue gas subchannel part 11A³ and a fourth flue gas sub channel part 11A⁴ locatedtherebeneath, respectively. These water channel parts 21 are located,for instance, adjacent the bends 11B. In a comparable manner, in thesecond and fourth bend 15B, 15D of the second part 4, channel parts 21are provided at a distance D from each other, between the second fluegas sub channel part 11A² and a third flue gas sub channel part 11A³located therebeneath and between, at least under, the fourth flue gassub channel part 11A⁴ and a fifth flue gas sub channel part 11A⁵ locatedtherebeneath, respectively. The channel parts are therefore always incommunication by at least one, and in most cases, two flue gas subchannel parts 11A¹-11A⁵, for optimal heat exchange.

With this heat exchanger, the burner deck is at an angle α relative tothe plane V, for instance between 20 and 85°. In the exemplaryembodiment shown, this angle is approximately 30°.

As clearly appears from the Figures, in the bends 11B, further heattransfer increasing elements 20A can be provided, in the form of, forinstance, ridges, projections or fins, whose intermediate passages arefor instance disposed in the flow direction of the flue gases, or at anangle thereto. These heat transfer increasing elements 20A which canalso be utilized in the other or alternative embodiments, form, inprinciple, a porous surface, viewed in flow direction of the flue gases.In a frontal surface, at right angles to the flow direction, theelements 20A preferably form at least approximately 70% of this surfaceso that the passages therebetween form less than 30%. More particularly,preferably 70% of the volume of the volume described by the elements 20Ais filled by the material of the elements 20A. The minimal measuredthicknesses/cross-sections of the portion of the surface that is notporous, is greater than 3 mm, preferably greater than 5 mm or 1 cm,respectively.

In FIGS. 5 and 6, schematically and in perspective view, a part 3 of aheat exchanger according to FIGS. 1 and 2 and FIGS. 3 and 4,respectively, are represented, viewed from the flue gas side 17. In FIG.5A, schematically, a side view of a portion of an element 20 is shown,in which fibers 40 are clearly recognizable, which can form a regularor, as shown, an irregular pattern and define continuous pores 41. FIG.5B schematically shows, in side view, a portion of an element 20, inparticular manufactured through metal foaming, wherein material 42 isclearly recognizable, in which continuous pores 41 are recognizable.Preferably, the metal foams are made of aluminum of an aluminum alloy.

FIGS. 5C and D schematically show alternative embodiments of a heattransferring element 20 in two views at right angles to each other,which element 20 comprises a series of profile parts 45 which form atleast an undulating and/or ribbed part 43. This part 43 or at least theprofile parts are preferably formed with ribs and/or undulations fromfolded and/or bent plate material, for instance steel or aluminum or aporous material, for instance a woven or non-woven fiber-based materialas described hereinabove. This undulating and/or ribbed part may havebeen formed from at least one plate or a series of plates which is orare folded such that always a channel 44 is confined by a plate part 45and a part, for instance wall 17, of the heat exchanger against whichthe part 43 is provided, which channel 44, in cross-section, preferablyhas a substantially triangular or trapezoid-shaped section and, in alongitudinal direction at right angles to said cross-section, has asomewhat meandering configuration, as is clearly visible in FIG. 5C, sothat each time, the flow direction of flue gases is changed and a goodheat exchange can take place.

Naturally, channels 44 in a part 43 according to FIGS. 5C and 5D canhave a different configuration, for instance less angularly undulating,or having acuter angles, of, for instance, 30, 45, 60 or 90 degrees ortherebetween. The channels 44 can have a main direction G1 which isapproximately parallel to the flow direction of flue gases HG1 from theburner chamber to the flue gas discharge, but can also include an anglethereto of, for instance, 30, 60 or 90 degrees, or therebetween. Severalparts 43 can be stacked on top of each other, for obtaining a largerelement 20, while the main direction of the channels of a underlyingplate can, each time, be turned relative to the main direction S of anoverlying plate, so that the through-flow of flue gases is hardlyadversely affected, if at all. The angle of torsion can, for instance,be some degrees to some tens of degrees, or more. The parts 43 can havethe plate parts 45 facing each other or even abutting each other, butcan also, each time be, separated by, for instance, a plate 46,preferably a porous plate.

In FIG. 7, a heat exchanger according to FIGS. 1 and 2 is shown as anexample while, however, a second water carrying channel 26 is provided.Thereto, grooves 27 and/or ribs 28 are provided on the parts 3, 4,between the first water carrying channel parts 21, for forming recessesin which a pipe 29 such as a metal or plastic pipe is secured, forinstance through clamping, form-closing, gluing, welding or in anothermanner. The second water carrying channel 26 can be used for, forinstance, tap water. The second (or, optionally, further) water carryingchannel 26 can, for that matter, also be integrally formed into theparts 3, 4 comparable to, for instance, the first channel 22, if theused material allows this or, for instance, when the water or othermedium to be heated therein is not used for consumption but for anindirectly heated boiler, floor or wall heating or the like. Preferably,the grooves and/or ribs extend parallel to the water carrying channelparts 21, so that extrusion is possible in simple manner.

As indicated, parts 3, 4 can be advantageously formed through extrusion,separately or jointly. With it, a relatively simple and economicallyadvantageous production of such heat exchangers is possible. However,naturally, also other production manners can be utilized, such ascasting, injection moulding and/or removing, so that somewhat morecomplex shapes become possible.

Preferably, the parts 3, 4 can be separated relatively easily, so thatcleaning is simplified. To that end, the parts 3, 4 can be mutuallyscrewed or clamped. This holds in particular also for the lowest,condensing part.

In FIG. 8, in top plan view, schematically, a portion of a heatingapparatus 25 with a heat exchanger according to the invention is shown,in a highly simplified manner, connected to two heating circuits. Afirst heating circuit 30 is, for instance, a space heating circuit withradiator 36, connected to the water carrying channel 22, in which afirst pump 31 is provided. A second heating circuit 32 is, for instance,a tap water heating circuit with tap 37 and, optionally, a second pump33. A supply device for, for instance, gas and air is connected to theburner chamber 5, for forming a premix burner. Naturally, only gas oranother fuel can also be supplied. Adjacent the underside of the heatingapparatus 25, to the flue gas passage 11, a condensation discharge 34 aswell as a flue gas discharge 35 may be connected.

It will be clear that also in other types of heat exchangers than in theexemplary embodiments shown, in one or more flue gas channels, a porousmaterial or element can be included for increasing the heat transferringsurface. The porosity can also, for instance, decrease in the flowdirection of the flue gases, i.e. in the direction of the flue gasdischarge, so that, at the beginning of the flue gas channel, hottergases will flow through faster and, according as they cool down, thethrough-flow will be somewhat delayed. Many variations thereon arepossible through variation of, for instance, the porosity, thethrough-flow surface, the extent to which the flue gas channel is filledwith porous material and/or the porous elements and the like.

It will be clear that combinations of parts of the embodimentsrepresented are also understood to be represented here.

The invention is not limited in any manner to the embodimentsrepresented in the description and the drawings. Many variations thereonare possible within the framework of the invention as outlined by theclaims. For instance, the meandering parts of the heat exchanger canhave a different design and materials other than aluminum or an aluminumalloy can be utilized, for instance other (lighter) metals or ceramicmaterials. More or fewer water carrying channel parts may be provided,while the number of bends and the shape thereof can be adjusted to, forinstance, the desired capacity. Instead of the burner with burner deckshown, a different burner can be utilized, for instance a known premixburner, which can be directly connected to the flue gas channel, inparticular within the embodiment of the first flue gas sub channel partas shown in FIGS. 3 and 4, which part can then, optionally, function asa part of the burner chamber. The flue gas channel can have a decreasingor, conversely, increasing passage in the direction of the flue gasdischarge, in order to influence the speed of the flue gases and, hence,the heat exchange.

The invention relates to a heat exchanger.

It is known from practice to manufacture heat exchangers for, forinstance, heating apparatus, hot water supplies and the like from, forinstance, steel or iron or light metal such as aluminum. As a rule, acasting method is applied here. Casting techniques offer a relativelylarge design choice but complex casting moulds. As a rule, in existingheat exchangers, heat transfer increasing elements are provided in aflue gas channel, which elements are cast integrally in the castingmoulds, at least when casting techniques are used. The heat transfer isthen not always optimal.

The object of the invention is to provide a heat exchanger.

In a first aspect, a heat exchanger according to the invention ischaracterized in that a body is provided with at least one flue gaschannel and at least one water carrying channel, at least one burnerchamber and at least one flue gas discharge, wherein the at least oneflue gas channel extends at least partly between the at least one burnerspace and at least one flue gas discharge, and at least one portion ofthe at least one flue gas channel comprises at least one porous or gastransmissive heat exchange element.

Herein, a porous or gas transmissive heat exchange element is understoodto mean an element with a structure and/or manufactured from a materialwith continuous openings, such that gas can flow through the heatexchange element(s), from, in flow direction, a side proximal to theburner space to a side proximal to the flue gas discharge. The openingscan comprise, for instance, pores and/or channels.

Preferably, in the flow direction of the flue gases, the porosityincreases and/or the density decreases of the heat exchange element or,if several heat exchange elements or parts thereof are providedsuccessively in the flow direction, of the successive heat exchangeelements, or parts thereof, so that the flow resistance decreases andthe heat transfer can be further optimized. For instance, a first partof the heat exchange element, or with several successive elements, afirst heat exchange element, adjacent the burner space, can have arelatively low porosity and high density, for instance a density of morethan 70%, while a second part of the heat exchange element or, in flowdirection, a trailing second heat exchange element, can have arelatively low density and high porosity, for instance a porosity ofmore than 70%. Preferably, especially in this manner, at least twosuccessive zones are formed in the flue gas channel, with differentaverage porosity and/or density. These values mentioned should not betaken as being limitative in any manner and serve merely as an example.On the basis of the further design of a heat exchanger, a skilled personcan chose and calculate suitable values.

Independently of the first aspect of the invention, and according to asecond aspect, the invention provides a first part of a heat exchangeelement wherein the minimal thicknesses and/or cross-sections of the atleast one heat exchange element of the first part are, in fact, greaterthan those of the at least one heat exchange element of the second part.This serves the purpose of providing a more massive first heat exchangeelement, which can resist the high temperatures of the combustion gases.

In a third aspect, a heat exchanger according to the invention ischaracterized in that the or at least one heat exchange element ismanufactured at least partly utilizing metal foaming. Preferably, theentire, or all heat exchange elements that are placed in a flue gaschannel are manufactured utilizing metal foaming.

Alternatively or additionally, the at least one heat exchange elementcan comprise fibers, in particular metal fibers.

Such fibers can be from, for instance, metal or ceramics and beprocessed into a porous mass, for instance a woven or non-woven element.The fibers ensure a relatively large contact surface in relation to thevolume, in particular if the fibers are relatively thin, for instance anaverage thickness of less than 1 micrometer to a few tens or hundreds ormicrometers. Preferably, the fibers have an average thickness of between0.5 and 200 micrometer, more particularly between 0.5 and 50 micrometer.

In an advantageous manner, a heat exchange element can be utilized thatis at least partly wintered.

In a fourth aspect, a heat exchanger according to the invention ischaracterized in that body parts are provided which are manufactured atleast partly through extrusion or through casting techniques. Lightmetal, such as aluminum or an alloy thereof, can then be utilized.

In a fifth aspect, the invention is characterized in that at least one,and preferably each body part is provided with recesses, in particularon a side remote from the flue gas channel, in which parts of a secondwater carrying channel part are formed or included.

The aspects mentioned and other aspects of the invention can be utilizedseparately as well as in combination.

The invention further contemplates providing a body part for such a heatexchanger, and a heat exchange element therefore.

The invention furthermore contemplates providing a method for themanufacture of a heat exchanger.

In a first aspect, a method is characterized in that at least two bodyparts are formed, in particular through extrusion or casting techniques,which body parts each comprise at least a portion of a water carryingchannel part, which body parts are mutually connected by end partsand/or at least one heat exchange element, such that the body parts arethus held at a mutual distance from each other while forming a flue gaschannel in which said at least one heat exchange element extends, andpreferably the water carrying channel parts in the two body parts aremutually connected.

Alternatively, one body part can be utilized in which the entire fluegas channel is formed, which is at least partly filled with at least oneat least partly porous or otherwise gas transmissive heat exchangeelement.

The invention will be further elucidated on the basis of exemplaryembodiments, with reference to the drawing. In the drawing:

FIGS. 1A and B show, in front and side view, a heat exchanger withoutside parts;

FIG. 2 shows, in perspective view, a heat exchanger according to FIG. 1;

FIG. 2A shows, in slight enlargement, a part of a heat exchangeraccording to FIG. 2;

FIG. 3 shows, in front view, a heat exchanger, in a second embodiment,without side parts;

FIG. 4 shows, in perspective side view, a heat exchanger according toFIG. 3;

FIG. 4A shows, in slight enlargement, a portion of a heat exchangeraccording to FIG. 4;

FIG. 5 shows, in perspective view, a body part for a heat exchangeraccording to FIGS. 1-2;

FIGS. 5A and 5B show embodiments of a heat transferring elementaccording to the invention;

FIGS. 5C and 5D schematically show, in side view and front view, analternative embodiment of a heat transferring surface increasingelement;

FIG. 6 shows, in perspective view, a body part for a heat exchangeraccording to FIGS. 3-4;

FIG. 7 shows, in side view, an alternative embodiment of a heatexchanger according to FIG. 1; and

FIG. 8 schematically shows a heating apparatus with a heat exchanger, inparticular according to FIG. 7.

The invention is described on the basis of a number of embodimentsthereof. These are not to be construed to be limitative in any manner.In particular, also, combinations or parts of the embodiments shown andloose parts thereof are understood to fall within the invention.Furthermore, variations thereon are understood to be also representedherein.

In FIG. 1A, in front view, and in FIG. 1B in side view, as well as inFIG. 2, a body 1 of a heat exchanger 1 is shown, assembled from two bodyparts 3, 4 and a burner hood 5 with burner deck 6. The body parts 3, 4and preferably also the burner hood 5 are preferably manufactured fromaluminum or an alloy thereof, although they can also be manufacturedfrom other material, such as iron or steel. In an advantageousembodiment, the body parts 3, 4 are manufactured substantially throughextrusion. This is a simple and relatively inexpensive manufacturingmethod. However, casting is an option too. Especially in the extrudedembodiment, the body parts 3, 4 have a substantially constantcross-section in one direction, in FIGS. 1A and 3 at right angles to theplane of the drawing.

In FIG. 1, adjacent a first end 7 of the body 2, the burner hood 5 issecured, for instance by screws 8, while the burner deck 6 is confinedbetween the burner hood 5 and two flanges 9 extending in two directionsat the end 7. Optionally, a suitable gasket (not shown) may have beeninserted for a flue gas-tight sealing. In the burner hood 5, a centralopening 10 is provided, through which, during use, gas or a gas/airmixture can be introduced to be burned, so that heated flue gases areobtained, formed in a flue gas channel 11 between the two body parts 3,4 as will be described hereinafter.

In this embodiment, the body 2, in particular the body parts 3, 4 eachcomprise a first part 12 and a second part 13, which here, link up witheach other. The first part 12, viewed in front view as in FIG. 1A, has ameandering configuration. To that end, each of the body parts 3, 4comprises a series of bends 14, in the embodiment shown four bends14A-D, 15 A-D, respectively. In this embodiment, the meanderingconfiguration is designed so as to be somewhat sinusoidal. Each bodypart has an outside 16 and an opposite side 17 proximal to the flue gaschannel 11. The meandering first part can therefore have elevations 18and lows 19. Here, as elevations 18 are seen the parts located furthestfrom a central plane V, and, as lows, the parts located therebetween. Ascentral plane V, a plane V can be seen, extending approximately midwaybetween two imaginary planes V1 and V2, with the planes V1 and V2extending parallel to each other over the elevations 18 located furthestfrom the plane V of the respective body parts 3, 4. In this first part,the configuration of the body parts 3, 4 and the channels 11 is, infact, a zigzag configuration so that a large heat transferring surfacecan be obtained in a compact space. It is noted that the first part 12can also have a different, for instance straight configuration, in thesense that no bends or meanderings are included, while the first part 12and the second part 13 have a parallel flow direction, or can mutuallyinclude an angle. Then, with the construction height remaining the same,in principle, the length of the flue gas channel 11 in the flowdirection from the burner space B to the flue gas discharge R will besmaller than in an embodiment where indeed a meandering part 12 isincluded, but a reduced flow resistance can be formed.

In this embodiment, the second part 13 of the each body part 3, 4 has asubstantially straight form, with an outside 16 and an opposite side 17proximal to the flue gas channel 11. In this embodiment, the plane Vextends midway between these two body parts 3, 4. However, this may alsobe offset over a distance relative therefrom, to the left or the right,in side view. On the side 17 proximal to the flue gas channel part 11,in the second part 13, on each body part 3, 4, one or a plurality ofheat transferring surface increasing element(s) 20 is/are present orprovided thereon, fastened thereon by, for instance, gluing, welding,forcing, clamping, sintering, soldering or fastened in a differentmanner, which element(s) form heat exchange elements. Also the or eachheat exchange element can be clamped between the two parts 3, 4. Theheat exchange element(s) extend(s) in the flue gas channel 11 and/orpartly define this, and are porous or gas transmissive such that, duringuse, flue gases can flow through the or each heat exchange element whileexchanging heat. As a result of the porosity or the gas transmissivityof the elements 20, a greater contact surface is obtained between heatedflue gases in the flue gas channel 11 and the surface 17 and/or heattransfer increasing elements provided thereon. If several heat exchangeelements are utilized, they can be placed both one behind the other andside by side in flow direction.

In the first part 12 of the flue gas channel 11 too, one or more heatexchange elements 20 can be provided, preferably with a porosity that ishigher than that of the or a heat exchange element 20 in the second part13.

Herein, porous is at least understood to include manufactured from amaterial and/or with a method such that open pores are provided that arein communication with each other and are, for instance, continuous.Herein, gas transmissive is at least understood to include an elementprovided with channels or such continuous openings through which fluegases can flow, while exchanging heat to the environment, in particularto the respective element, such as for instance foams, fins, fiber mat.The porosity and density can be expressed in a percentage, while withporosity, the percentage represents the part of the volume not filled bythe solid material such as metal and, hence, suitable for through-flowby flue gases. For the density, the percentage signifies the part formedby the solid material.

In an advantageous embodiment, the or each heat exchange element 20 isat least partly formed through metal foaming, as schematically shown inFIG. 5B, so that a porous mass is obtained that can be manufactured orbrought into a desired form, for instance by mechanical and/or removingoperations. With it, an optimal shape for the heat exchange elements canbe obtained, with optimal abutment against the inside 17 of the secondpart 13. Metal foam can offer a relatively robust element that may beconstructively advantageous and can ensure a good heat exchange betweenthe flue gases and the metal, and a good transfer to the elements 3, 4.As a technique, metal foaming is sufficiently known from practice, asare the means to then create and influence, for instance, porosity, sothat in each part of an element obtained through metal foaming, adesired predetermined porosity can be achieved, in any case on average.

In an alternative embodiment, fibers are used for the heat exchangeelement, as schematically shown in FIG. 5A, for instance metal fibers orceramic fibers. A woven or non-woven element can, for instance, beformed therefrom. In an alternative embodiment, the elements 20 can beat least partly formed by removing or non-removing operations of thebody parts or, when for instance a casting process is utilized forforming the body parts, through integral forming, in particular casting,during manufacture, while for forming the elements, gas can for instancebe blown through the liquid material. Also, ribs can be extruded.Alternatively or additionally, porous and/or gas transmissive materialscan be used, such as metals or ceramic filling materials. In thedrawing, the heat transferring surface increasing elements arerepresented in a simplified manner as rectangles. The design of suchelements can simply be selected by skilled person.

Fibers for an element 20 according to the invention can be at leastpartly manufactured through drawing or extrusion, in particular throughbundle drawing or multi fiber extrusion, through hot drawing from a weldpool, through cold or through hot rolling, a removing and/or pressingtechniques and/or through foaming or blowing. The or a heat exchangeelement can at least partly be manufactured from a woven or a non-wovenmaterial, for instance from fibers, in particular metals and/or ceramicfibers. It is preferred that a heat exchange element 20 according to theinvention is at least partly sintered, so that an element is obtainedwhich is heat and moisture resistant and can be placed as a unit.

In a heat exchanger according to the invention, use is preferably madeof zones that succeed each other in flow direction s, in which zones theheat exchange can be different. To that end, the porosity or density ofthe respective heat exchange element 20 or part thereof extending in arespective zone I, II, can deviate from that in a different zone. InFIG. 1, two zones I, II are shown. However, several zones can beprovided too and the first zone can for instance extend in the firstpart 12 and the second zone in the second part 13, as shown in FIG. 1,or both zones I, II can extend in the second zone 13 as shown in FIG. 3,with the first part 12 not comprising a porous heat exchange element. Byway of illustration, the first zone I can for instance have a porosityof less than 70%, and a relatively high density of, for instance, morethan 70%, for instance 95%, while then, the second zone II has, forinstance, a relatively low density, for instance less than 70%, and arelative high porosity, such as over 70%, more particularly for instance95%. As a result, the flow resistance will decrease in flow direction.In the first zone, during use, heated flue cases will give off thegreatest part of the heat, be cooled from, for instance, well over above1000° C., for instance approximately 1600° C., to well over 1000° C.,for instance to approximately 450° C. In the second zone, the heatexchange will be continued so that the flue gases can be cooled downfurther, for instance to a condensing temperature.

The use of metal foaming offers the advantage that a heat exchangeelement clamped only against the parts 3, 4 ensures a particularly goodheat transfer when compared to, for instance, fins or plate parts. Forobtaining a changing porosity and/or density, different heat exchangeelements with different porosities and/or densities can be placed sideby side and/or one behind the other, or the porosity and/or density in aheat exchange element can be varied.

In the first part 12 and the second part 13, parts 21 of a watercarrying channel 22 are provided. In the exemplary embodiment shown,these parts 21 are all tubular with a constant cross-section, which havea longitudinal direction L, approximately at right angles to the planeof the drawing in FIGS. 1A and 3, which longitudinal direction L isparallel to an extrusion direction for the body parts, if these areextruded. Adjacent the first end 7, in each body part 3, 4, a first part21A is provided as the beginning of the meandering first part 12,directly below the burner deck 6. Then, two parts 21B are provided inthe second part 13. Preferably, the channel parts 21 on both sides ofthe flue gas carrying channel 11 are mutually connected for forming achannel 22 circumventing the heat exchanger, but, optionally, thechannel parts on both sides of the flue gas carrying channel 11 canalso, each, form a channel part 22 that can be used for, for instance,different heat exchange circuits, or be mutually connected outside theheat exchanger 1.

In the channel parts 22, also, heat transferring surface increasingelements can be utilized which can be integrally formed especiallythrough extrusion, while the channel parts themselves need not bedivisible, while to that end, also, porous materials and/or elements canbe used as described hereinabove.

It is preferred that the channel parts 21 are mutually connected throughend hoods 24 and connecting channel parts extending therein (FIG. 8).These end hoods 24 may further comprise the connections for the heatingcircuits, gas and air supply pipes and the like. The end hoods cansimply be fastened, with interposition of suitable gaskets, against thesides of the parts 3, 4 arranged side by side, so that a flue gaschannel 11 closed towards the sides and a continuous water channel 22 orwater channels 22 are obtained, while furthermore, the parts 3, 4 areheld in a suitable position and at a suitable distance.

With the embodiment shown, the channel parts 21 are provided on theoutside of the parts 3, 4, so that the sides thereof facing inwards,i.e. towards the flue gas channel 11, can be designed to be relativelyflat, at least without protrusions formed by the channel parts. Theycan, however, also be positioned differently, for instance partlyoutside and partly inside the flue gas channel 11 or entirely inside theflue gas channel 11. This holds both for the individual channel partsand for the assembly thereof. Preferably, the or each channel 22 is laidout such that it can function in counterflow to the flow direction ofthe flue gases through the flue gas channel 11, so that an improvedefficiency can be obtained. To that end, for instance, the through-flowopening in the different channel parts can be adjusted in order togenerate a flow speed change in the channel, for a further optimisationof the heat exchange.

At the underside of the heat exchanger 1, a foot 23 is provided on whichthe heat exchanger can be mounted.

In FIGS. 3 and 4, an alternative embodiment is given of a heat exchangeraccording to the invention, wherein, substantially, only those parts aredescribed that deviate from the other embodiments. Further, reference ismade to the further description, in particular of FIGS. 1, 2 and 8. Inthis embodiment, each of the parts 3, 4 in the first part 12 has ameandering flow gas channel part 11A formed between bends 14A-D, 15A-Drespectively, formed such that five flue gas sub channel parts 11A¹-11A⁵are obtained, which are mutually connected by bend parts 11B and extendapproximately parallel to each other. In the first part 3, in the firstbend 14A, two water channel parts 21 are included, parallel to eachother, located at a distance D from each other, between a relativelywide first flue gas sub channel part 11A¹ linking up with the burnerdeck 6 of the burner 5 and a second flue gas sub channel part 11A²located therebeneath, respectively, and between a third flue gas subchannel part 11A³ and a fourth flue gas sub channel part 11A⁴ locatedtherebeneath, respectively. These water channel parts 21 are located,for instance, adjacent the bends 11B. In a comparable manner, in thesecond and fourth bend 15B, 15D of the second part 4, channel parts 21are provided at a distance D from each other, between the second fluegas sub channel part 11A² and a third flue gas sub channel part 11A3located therebeneath and between, at least under, the fourth flue gassub channel part 11A⁴ and a fifth flue gas sub channel part 11A⁵ locatedtherebeneath, respectively. The channel parts are therefore always incommunication by at least one, and in most cases, two flue gas subchannel parts 11A¹-11A⁵, for optimal heat exchange.

With this heat exchanger, the burner deck is at an angle α relative tothe plane V, for instance between 20 and 85°. In the exemplaryembodiment shown, this angle is approximately 30°.

As clearly appears from the Figures, in the bends 11B, further heattransfer increasing elements 20A can be provided, in the form of, forinstance, ridges, projections or fins, whose intermediate passages arefor instance disposed in the flow direction of the flue gases, or at anangle thereto. These heat transfer increasing elements 20A which canalso be utilized in the other or alternative embodiments, form, inprinciple, a porous surface, viewed in flow direction of the flue gases.In a frontal surface, at right angles to the flow direction, theelements 20A preferably form at least approximately 70% of this surfaceso that the passages therebetween form less than 30%. More particularly,preferably 70% of the volume of the volume described by the elements 20Ais filled by the material of the elements 20A. The minimal measuredthicknesses/cross-sections of the portion of the surface that is notporous, is greater than 3 mm, preferably greater than 5 mm or 1 cm,respectively.

In FIGS. 5 and 6, schematically and in perspective view, a part 3 of aheat exchanger according to FIGS. 1 and 2 and FIGS. 3 and 4,respectively, are represented, viewed from the flue gas side 17. In FIG.5A, schematically, a side view of a portion of an element 20 is shown,in which fibers 40 are clearly recognizable, which can form a regularor, as shown, an irregular pattern and define continuous pores 41. FIG.5B schematically shows, in side view, a portion of an element 20, inparticular manufactured through metal foaming, wherein material 42 isclearly recognizable, in which continuous pores 41 are recognizable.Preferably, the metal foams are made of aluminum of an aluminum alloy.

FIGS. 5C and D schematically show alternative embodiments of a heattransferring element 20 in two views at right angles to each other,which element 20 comprises a series of profile parts 45 which form atleast an undulating and/or ribbed part 43. This part 43 or at least theprofile parts are preferably formed with ribs and/or undulations fromfolded and/or bent plate material, for instance steel or aluminum or aporous material, for instance a woven or non-woven fiber-based materialas described hereinabove. This undulating and/or ribbed part may havebeen formed from at least one plate or a series of plates which is orare folded such that always a channel 44 is confined by a plate part 45and a part, for instance wall 17, of the heat exchanger against whichthe part 43 is provided, which channel 44, in cross-section, preferablyhas a substantially triangular or trapezoid-shaped section and, in alongitudinal direction at right angles to said cross-section, has asomewhat meandering configuration, as is clearly visible in FIG. 5C, sothat each time, the flow direction of flue gases is changed and a goodheat exchange can take place.

Naturally, channels 44 in a part 43 according to FIGS. 5C and 5D canhave a different configuration, for instance less angularly undulating,or having acuter angles, of, for instance, 30, 45, 60 or 90 degrees ortherebetween. The channels 44 can have a main direction G1 which isapproximately parallel to the flow direction of flue gases HG1 from theburner chamber to the flue gas discharge, but can also include an anglethereto of, for instance, 30, 60 or 90 degrees, or therebetween. Severalparts 43 can be stacked on top of each other, for obtaining a largerelement 20, while the main direction of the channels of a underlyingplate can, each time, be turned relative to the main direction S of anoverlying plate, so that the through-flow of flue gases is hardlyadversely affected, if at all. The angle of torsion can, for instance,be some degrees to some tens of degrees, or more. The parts 43 can havethe plate parts 45 facing each other or even abutting each other, butcan also, each time be, separated by, for instance, a plate 46,preferably a porous plate.

In FIG. 7, a heat exchanger according to FIGS. 1 and 2 is shown as anexample while, however, a second water carrying channel 26 is provided.Thereto, grooves 27 and/or ribs 28 are provided on the parts 3, 4,between the first water carrying channel parts 21, for forming recessesin which a pipe 29 such as a metal or plastic pipe is secured, forinstance through clamping, form-closing, gluing, welding or in anothermanner. The second water carrying channel 26 can be used for, forinstance, tap water. The second (or, optionally, further) water carryingchannel 26 can, for that matter, also be integrally formed into theparts 3, 4 comparable to, for instance, the first channel 22, if theused material allows this or, for instance, when the water or othermedium to be heated therein is not used for consumption but for anindirectly heated boiler, floor or wall heating or the like. Preferably,the grooves and/or ribs extend parallel to the water carrying channelparts 21, so that extrusion is possible in simple manner.

As indicated, parts 3, 4 can be advantageously formed through extrusion,separately or jointly. With it, a relatively simple and economicallyadvantageous production of such heat exchangers is possible. However,naturally, also other production manners can be utilized, such ascasting, injection moulding and/or removing, so that somewhat morecomplex shapes become possible.

Preferably, the parts 3, 4 can be separated relatively easily, so thatcleaning is simplified. To that end, the parts 3, 4 can be mutuallyscrewed or clamped. This holds in particular also for the lowest,condensing part.

In FIG. 8, in top plan view, schematically, a portion of a heatingapparatus 25 with a heat exchanger according to the invention is shown,in a highly simplified manner, connected to two heating circuits. Afirst heating circuit 30 is, for instance, a space heating circuit withradiator 36, connected to the water carrying channel 22, in which afirst pump 31 is provided. A second heating circuit 32 is, for instance,a tap water heating circuit with tap 37 and, optionally, a second pump33. A supply device for, for instance, gas and air is connected to theburner chamber 5, for forming a premix burner. Naturally, only gas oranother fuel can also be supplied. Adjacent the underside of the heatingapparatus 25, to the flue gas passage 11, a condensation discharge 34 aswell as a flue gas discharge 35 may be connected.

It will be clear that also in other types of heat exchangers than in theexemplary embodiments shown, in one or more flue gas channels, a porousmaterial or element can be included for increasing the heat transferringsurface. The porosity can also, for instance, decrease in the flowdirection of the flue gases, i.e. in the direction of the flue gasdischarge, so that, at the beginning of the flue gas channel, hottergases will flow through faster and, according as they cool down, thethrough-flow will be somewhat delayed. Many variations thereon arepossible through variation of, for instance, the porosity, thethrough-flow surface, the extent to which the flue gas channel is filledwith porous material and/or the porous elements and the like.

It will be clear that combinations of parts of the embodimentsrepresented are also understood to be represented here.

The invention is not limited in any manner to the embodimentsrepresented in the description and the drawings. Many variations thereonare possible within the framework of the invention as outlined by theclaims. For instance, the meandering parts of the heat exchanger canhave a different design and materials other than aluminum or an aluminumalloy can be utilized, for instance other (lighter) metals or ceramicmaterials. More or fewer water carrying channel parts may be provided,while the number of bends and the shape thereof can be adjusted to, forinstance, the desired capacity. Instead of the burner with burner deckshown, a different burner can be utilized, for instance a known premixburner, which can be directly connected to the flue gas channel, inparticular within the embodiment of the first flue gas sub channel partas shown in FIGS. 3 and 4, which part can then, optionally, function asa part of the burner chamber. The flue gas channel can have a decreasingor, conversely, increasing passage in the direction of the flue gasdischarge, in order to influence the speed of the flue gases and, hence,the heat exchange.

1. A heat exchanger, provided with a body with at least one flue gaschannel and at least one water carrying channel, at least one burnerspace and at least one flue gas discharge, wherein the at least one fluegas channel extends at least partly between at least a burner space andat least one flue gas discharge, and at least a portion of the at leastone flue gas channel comprises at least one porous or gas-transmissiveheat exchange element.
 2. A heat exchanger according to claim 1, whereinthe gas transmissivity of the or each heat exchange element in thedirection away from the at least one burner space varies.
 3. A heatexchanger according to claim 2, wherein a first heat exchange element orfirst part of a heat exchange element is provided, adjacent a burnerspace, with a relatively low porosity and relatively high density, and asecond heat exchange element or second part of a heat exchange elementis provided, on a side of the respective burner space remote from saidfirst heat exchange element or first part thereof, with a relativelyhigh porosity and relatively low density.
 4. A heat exchanger accordingto claim 1, wherein at least a part of the or a heat exchange element isat least partly manufactured through metal foaming, in particular metalfoam from aluminum or an aluminum alloy.
 5. A heat exchanger accordingto claim 1, wherein the at least one heat exchange element is includedbetween at least a first and a second body part of the body.
 6. A heatexchanger according to claim 1, wherein the body parts each comprise atleast a first part with a meandering configuration, which body parts arepositioned relative to each other such that the meandering parts engageeach other at least partly and therebetween a first part of the flue gaschannel is formed, wherein each body part comprises at least a portionof the at least one water carrying channel, wherein said first part ofeach body part comprises at least a first and a second bend, wherein thefirst bend of a first body part reaches into the first bend of thesecond body part and the second bend of the second body part reachesinto the second bend of the first body part and/or in each first part ofa body part and preferably, in each bend therein, at least a part ofsaid at least one water carrying channel is provided.
 7. A heatexchanger according to claim 1, wherein the heat exchange elementcomprises fibers, in particular metal fibers.
 8. A heat exchangeraccording to claim 1, wherein the or a heat exchange element is at leastpartly manufactured from a woven or a non-woven material.
 9. A heatexchanger according to claim 1, wherein fibers are used in the or a heatexchange element with an average diameter between 0.5 and 200micrometers, more particularly between 0.5 and 50 micrometers.
 10. Aheat exchanger according to claim 1, wherein the or a heat exchangeelement has a porosity of between 75 and 97%.
 11. A heat exchangeraccording to claim 1 wherein the or a heat exchange element comprises atleast an undulating and/or ribbed part, in particular ribbed and/orundulating formed from folded and/or bent plate material or fiber platematerial.
 12. A heat exchanger according to claim 11, wherein saidundulating and/or ribbed part is formed from at least one plate or aseries of plates which is or are folded such that, each time, a channelis confined by a plate part and a part of the heat exchanger againstwhich the part is provided, which channel, in a cross section,preferably has a substantially triangular or trapezoidal section and, ina longitudinal direction at right angles to said cross-section, has asomewhat meandering configuration.
 13. A heat exchanger according toclaim 1, wherein in a first part of each body part at least two bendsare provided which engage in or engage around a bend in an adjoiningfirst part of the other body part, wherein the bends are formed suchthat they each cut a plane located midway between two parallel planesdefined by the outsides of the bends which are located furthest apart inthe respective first parts, measured in a direction at right angles tosaid parallel planes, while, during use, flue gases flow between saidengaging bends of the body parts.
 14. A heat exchanger according toclaim 1, wherein at least one, and preferably each body part is providedwith recesses, in particular on a side remote from the flue gas channel,in which parts of a second water carrying channel are formed orincluded.
 15. A heat exchanger according to claim 14, wherein said partsof the second water carrying channel are provided, in particularclamped, in said recesses.
 16. A heat exchanger according to claim 1,wherein body parts are manufactured substantially through extrusion. 17.A heat exchanger according to claim 16, wherein as heat transferringsurface increasing elements heat exchange elements are provided on atleast a part of at least one of the body parts, which elements areformed as separately provided elements and/or through removingoperations of the extruded body parts.
 18. A heat exchanger according toclaim 1, wherein the body parts and the heat exchange elements are atleast partly manufactured from aluminum or an aluminum alloy.
 19. A heatexchanger according to claim 1, wherein in a first part of the flue gaschannel heat transferring surface increasing elements are provided, inparticular fins, projections and/or ridges, and, in a second part, atleast one porous or gas transmissive heat exchange element.
 20. A bodypart for a heat exchanger according to claim
 1. 21. A body partaccording to claim 20, wherein the body part comprises at least a firstpart with a meandering configuration, wherein each body part comprisesat least a portion of the at least one water carrying channel and, inaddition to at least a part of said portion of the water carryingchannel, is provided on a part forming the flue gas channel wall withheat transferring surface increasing elements.
 22. A body part accordingto claim 20, substantially formed through extrusion.
 23. A heat exchangeelement for use in a heat exchanger according to claim 1, preferably atleast partly manufactured through metal foaming.
 24. A method forforming a heat exchanger, wherein at least two body parts are formed, inparticular through extrusion or casting techniques, which body partseach comprise at least a portion of a water carrying channel part, whichbody parts are mutually connected by end parts and/or at least one heatexchange element in a manner such that the body parts are thus held at amutual distance from each other while forming a flue gas channel inwhich said at least one heat exchange element extends and preferably thewater carrying channel parts in the two body parts are mutuallyconnected.
 25. A method according to claim 24, wherein the at least oneheat exchange element is at least partly manufactured through metalfoaming or from fibers.
 26. A heating apparatus, provided with a heatexchanger according to claim 1.